ABOUT THE PRODUCT
Spool Performance – Mercedes 725 9G FX-RT Upgraded Clutch Kit
Rated for up to 1,700 Nm input torque
The Mercedes 725 9G transmission is a strong unit from the factory—but once torque levels push past the mid-700 Nm, the stock frictions and limited plate counts begin to slip, especially under repeated high-load, high-temperature conditions.
Spool Performance has developed a complete upgraded clutch system for the 725 9G using our FX-RT high-coefficient, high-energy friction material, the same proven technology that transformed the 8HP50 platform into a competition worthy transmission.
This new kit increases both the coefficient of friction (+20%) and the clutch counts across all six elements, dramatically increasing the torque capacity of every gear.
Clutch Count Increases
| Clutch | Stock | Upgraded | Increase |
|---|---|---|---|
| A | 4 | 6 | +2 |
| B | 4 | 7 | +3 |
| C | 5 | 7 | +2 |
| D | 6 | 9 | +3 |
| E | 6 | 9 | +3 |
| F | 7 | 10 | +3 |
Combined with the FX-RT friction upgrade, the resulting torque-capacity increases are substantial.
Torque Capacity Gains (Per Gear)
Based on clutch engagement logic for the 9G and the combined friction + plate-count increases:
| Gear | Engaged Clutches | Torque Increase |
|---|---|---|
| 1st | B C E | +68% |
| 2nd | C D E | +68% |
| 3rd | B C D | +68% |
| 4th | B C F | +68% |
| 5th | B D F | +71.4% |
| 6th | D E F | +71.4% |
| 7th | B E F | +71.4% |
| 8th | A E F | +71.4% |
| 9th | A B F | +71.4% |
Final Torque Rating
The factory 725 9G is rated for 1000 Nm.
With the FX-RT clutch packs installed:
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1st–4th gear clutch-limited rating: ≈1680 Nm
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5th–9th gear clutch-limited rating: ≈1714 Nm
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Overall clutch-pack system capability: ≈1,700 Nm
This upgrade raises the clutch-limited torque threshold by +68–71%, depending on gear.
Why FX-RT?
Our FX-RT friction material was engineered specifically for high-torque, high-energy, fast-shift transmissions. It has been proven in our 8HP50 kits, where customers reliably push 900–1000 Nm. Now the same technology elevates the Mercedes 725 9G into a new performance class.
Benefits include:
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20% higher μ for dramatically improved static and dynamic holding power
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Higher thermal stability under repeated high-load upshifts
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Reduced shift flare and reduced clutch slip
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Smoother, more consistent clutch apply characteristics
Who This Kit Is For
The Spool Performance 725 9G upgraded clutch kit is ideal for:
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High-power M177 builds
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GLE63 / GLS63 high-boost setups
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Tuned E63 / S63 running hybrid turbos
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Track-driven or heavy-use AMG applications
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Anyone targeting 1000+ crank hp with headroom
Your 725 9G is no longer the limiting factor. With Spool Performance FX-RT friction technology and increased clutch capacity, the transmission becomes capable of safely holding ~1700 Nm, giving your AMG the drivetrain headroom it needs to push big-power, high-boost builds confidently and repeatedly.
What’s Included
The Spool Performance 725 9G FX-RT Clutch Upgrade Kit includes all components required for a complete drop-in installation. No machining or custom fabrication is needed.
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Clutch A [B08] Pack (6-plate upgrade)
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6 x FX-RT friction discs
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6 x Upgraded Steel plates
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1 x Custom Pressure Plate
Clutch B [B05] Pack (7-plate upgrade)
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7 x FX-RT friction discs
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7 x steel plates
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1 x Custom Pressure Plate
Clutch C [B06] Pack (7-plate upgrade)
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7 x FX-RT friction discs
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7 x steel plates
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1 x Custom Pressure Plate
Clutch D [K81] Pack (9-plate upgrade)
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9 x FX-RT friction+steel internal spline discs
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9 FX-RT friction+steel external spline discs
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1 x Custom Pressure Plate
Clutch E [K38] Pack (9-plate upgrade)
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9 x FX-RT friction discs
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9 x steel plates
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1 x Custom Pressure Plate
Clutch F [K27] Pack (10-plate upgrade)
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10 x FX-RT friction discs
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10 x steel plates
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1 x Custom Pressure Plate
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Everything is pre-measured and packaged by clutch pack to ensure consistent clearances and simplified assembly. The kit is fully compatible with factory drums, pistons, and snap-ring locations.
Note: Please email customer_service@spoolperformance.us for details on scheduling training for installation of this component.
When will my order ship?
If it’s in stock and the order is placed before 3pm, it ships the same day. If you ordered a product with ceramic coating, it will ship the following business day.
If the product or color spec you’re looking for is not in stock, you can join the waitlist by clicking the “email when available” button underneath the “out of stock” label. We will email you as soon as your product is available and give you an estimated back in stock time.
What if I submitted a custom order?
If you are making a custom order, email us to submit your request and we will give you an estimated delivery time based on the special manufacturing time.
What if my product arrives damaged, incorrect, or is missing parts?
If you received the incorrect product or color, missing parts, or the item is defective, email us a picture with your order number and you will receive a refund or exchange. Contact us at info@shopprojectgamma.comand we will work with you to make it right.
What if I’m not satisfied with the product?
If the product is unused and uninstalled, we can offer you a refund, exchange, or store credit. If the product was used or installed on your vehicle, we unfortunately cannot offer any refund, exchanges, or credit.
What if I installed my products and then I decide I don’t like them?
Unfortunately used or installed products will not qualify for a return or refund. If you have any questions or concerns you can email us at info@shopprojectgamma.com
A restocking fee of 20% of the original purchase price may be applied to returned products. This fee covers the costs associated with processing the return and restocking the item if applicable. Please refer to our policies page for more info regarding all exchanges and returns.
Have a question you don't see answered here? Email us at info@shopprojectgamma.com and we'll get back to you.
